Electric railway.



Patented Dec. I6, I902.

yv. B. POTTER. ELECTRIC RAILWAY.

(Application filed Apr. 28, 1900.)

(No Model.)

Jnventort- William Spotter UNITED STATES PATENT OFFICE.

WILLIAM I3. POTTER, OF SOI-IENEOTADY, NEW YORK, ASSIGNOR TO THE GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC RAILWAY.

SPECIFICATION forming part of Letters Patent No. 716,101, dated December16, 1902.

Application filed April 28,1900. $erial No. 14,660- (No model.)

To all whom, it non/y concern/.-

Be it known that 1, WILLIAM B. POTT R, a citizen of the UnitedStates,residing at Schenectady, in the county of Schenectady and Stateof New York, have invented certain new and useful Improvements inElectric Railways, (Case No. 1,641,) of which the following is adescription.

My present invention relates to an electricrailway system, and in someof its aspects more particularly to that type which makes use ofalternating current for its motive power.

It comprises certain means wherebyan operator on a car may cause theworking conductors constituting the conducting system through whichcurrent is fed to a motor or motors to be supplied with current from anyone of a number of sources, whereby the motor or motors on the car maybe caused to run at suitable speeds or to start from or come to restthrough suitable gradations in speed.

Other advantages flowing from the use of my invention will be apparentby reference to the following description, taken in connection with theaccompanying drawings, while the scope of the invention, both in itsbroad and narrow features, will be particularly pointed out in theappended claims.

In organizing an electric railway to operate in accordance with myinvention I prefer in cases where'the railroad is of considerable lengthto divide the working conductors up into sections. Some of thesesections, such as those corresponding to portions of the road where nostops are to be made, are supplied by alternating current at a certainfrequency, while other sections corresponding to pertions of the roadalong which stops are to be made are arranged to be supplied withcurrents of a frequency controllable at the will of the operator on thecar. For purposes of economy as well as convenience I find it preferableto supply the railroad as a whole by means of energy derived from asingle central station and to obtain alternating currents of differentfrequencies by suitably transforming the current derived from the mainsource. 'It will of course be understood that my preference in thisrespect is not to be construed as a limitation, since it will beevisections of the conducting system and other sources similarlyconnected.

The means which I employ for controlling the frequency ofcurrentsupplied to the working conductors will be better comprehended bydescribing the same in connection with the accompanying drawings, whichillustrate diagrammatically one embodiment of my invention.

At 1 I have indicated a source of electrical energysuch, for example, asa three-phase alternating-current generator, the particular nature ofthe generating means being unimportant. Transmission-lines 2, 3, and 4extend therefrom and along the line of the railway. The breaks in thetransmission-lines 2, 3, and 4 are intended to indicate a transmission-line of considerable length, a portion of the same being shownin the drawings. The working conductors from which current is collectedand supplied to the motors on the railway-vehicles are indicated at 5and 6. These conductors 5 and 6 constitute a single section, an adjacentsection being shown at 7 8. The section 5 6 is supposed to represent aportion of the conducting system located near a station or otherstopping-place, while the section 7 8 corresponds, on the other hand, toa portion of the road on which no stops are normally made.

When the railway-vehicles are on portions of the line betweenstationssuch, for example, as those corresponding to the conductors 7Sthey are supposed to operate at full speed. The conductors 7 8 maytherefore be supplied with current of normal and invariable frequency,and to this end suitable connect-ions are made between thetransmissionlines 2 3 4 and the conductors 7 8. As illustrative of suchconnections, I have shown a step-down transformer 9, with primary andsecondary leads connected, respectively, to the transmission-lines 2, 3,and 4 and to the working conductors 7 and 8, one terminal of thesecondary being grounded to correspond with the ground connection of themotors representing the return-circuit for the threephase currentutilized by the motor.

ICO

The section comprising the conductors5 6, unlike the section comprisingthe conductors 7 8, is arranged to be supplied with currents ofdifferent frequencies, the particular means employed being shown in thedrawings partly in diagram and partly by pictorial representation. Thealternating currents of different frequencies may be separatelygenerated or produced in a great many other ways; but for the presentpurpose I propose to use a generating means consisting of a motorsupplied with current from the transmissionlines 2, 3, and 4 andmechanically connected to a number of generators in such a way as tosecure suitable gradations of frequency in the currents produced by saidgenerators. In the drawings I have indicated the motor at 10 and itsconnections with the transmission-lines 2, 3, and 4 by means of the conductors 11, 12, and 13, these conductors being led into the armature ofthe motor in a well-understood manner. The motor which I prefer toemploy is of the synchronous type, having its field excited by directcurrent, the direct cnrrentin this instance being supplied over bus-bars14 15, fed from a small eXciter 16, which, if desired, may be driven bythe said motor. A number of generators 17 18 19 are mechanicallyconnected in any suitable manner to the driving-motor 10, thearrangements being such that the currents produced by the respectivegenerators vary in frequency. These generators may be directly connectedtogether and with the driving-motor, so that the shafts of all themachines constitute practially a single shaft, in which case thegenerators 17, 18, and 19 require in their construction differentnumbers of poles, so as to produce currents of different frequencies. Onthe other hand,a belted or geared connection between the generators andthe driving-motors maybe made in such a manner as to cause thegenerators to run at different speeds, in which case the generators neednot necessarily have different numbers of poles. In the drawings dottedlines are intended to represent suitable mechanical connections betweenthe machines. From what has been said it will be evident that manydifferent devices and adaptations may be employed for producing thealternating currents of the frequencydesired without departing from myinvention.

To make suitable connections between the generators of differentfrequency and the section of the supply system comprising the workingconductors 5 6 of the railway, I make use of a switch the movement ofwhich is controlled from an electric circuit which may be opened andclosed on the railway-vehicle as it moves along. In the instance shownthe switch is driven by a small inductionanotor 20, the circuits ofwhich are opened and closed by a relay device connected to acontrolling-conductor 21, extending along the line of the railwayparallel to the working conductors and with which a sliding contact ismade by means of a contact-shoe carried by the car.

One form of switching device which I find appropriate for carrying outmy invention consists of a cylinder mounted in suitable bearings, so asto revolve about its axis, and having thereon a series of angularly andprogressively displaced contacts adapted to successively engage aplurality of cooperating fixed contact-fingers. In the drawings theswitch-cylinder is shown at 22 and is indicated as provided with foursets of contacts, (numbered 23, 24, 25, and 26, respectively.) The rowof fixed contact-fingers is indicated by the line of small circles shownjust above the cylinder 22. Corresponding with the sets of contacts 23to 26, inclusive, there are for each set a pair of contact-fingersconnected, respectively, to leads 27 28, joined to the workingconductors 5 6. The other contactfingers are connected to sources ofalternating current of different frequencies and by the rotation of thecylinder 22 act through the intervention of the leads 27 28 to connectthe working conductors 5 6 with the different sources of alternatingcurrent.

In the system shown one of the threephase leads is grounded in allcases, so as to form a return conductor, so that in making connectionsonly two leads have to be considered. Thus, for example, in the case ofthe generator 17 one of its leads is grounded at G, while the other twolead to contact-fingers on the controlling-switch. In a similar way oneof the leads of each of the generators 18 19 is grounded, while theother terminals are connected to suitably-arranged contact-fingers onthe controlling-switch. Current of normal frequency is derived from thesecondary of a transformer 29, the primary of which is connected acrossthe transmission-lines 2, 3, and 4 and the secondary to leads 30 and 31,one of the secondary terminals being, however, grounded at G, as beforementioned. Branch conductors 32 and 33 lead to contactfingers on thecontrolling-switch.

By an inspection of the diagram it will readily be seen that as thecontrolling-switch is turned the fixed contacts 23 are first to engagetheir cooperating contact-fingers, thereby connecting the generator 17which is of the lowest frequency with the leads 27 28, which are joinedto the working conductors 5 6, thereby supplying the working conductorswith current of minimum frequency. As the controlling-switch continuesits movement the generator 17 is out out. of circuit and the generator18 substituted therefor, while upon still further movement the generator18 is cut out and that numbered 19 substituted. Upon completion of themovement of the controlling-switch the generator 19 is cut out ofcircuit and the working conductors connected across the secondary of thetransformer 29, thereby receiving current of the same frequency as thatflowing in the transmission-lines 2, 3, and 4. It is to be understoodthat the currents derived from the generators 17, 18, and 19 vary infrequency, as well as in voltage, in such a progression as to give thedesired rate of acceleration to the railway-vehicles as thecontrolling-switch is turned by means of its driving-motor.

The driving-motor (shown at 20) is mechanically connected with theswitch-cylinder 22 by means of a toothed gear 34 and a pinion 35, thoughit is to be understood that any suitable connection may be employed inplace thereof. This motor I prefer to make of the three-phase type, sothat it may be supplied directly from the three-phase circuits of therailway system. In order to lock the armature of the motor in anydesired position, I make use of some suitable form of clutch, that onewhich is shown in the drawings being of the magnetically-actuated type.The armature of the motor is provided with a disk 36, of magneticmaterial, mounted on the end thereof. In close proximity thereto is thecore of an electromagnet 38, carried by a standard fixed to thebase-plate of the motor. This magnet is shown as consisting of a fiatplate having a working face arranged close to the cooperating disk 36. Amagnetizingcoil 37 is embedded in the core of the electromagnet. Tosecure positive action, the working faces of the clutch may be toothed,ifdesired.

The circuits of the motor 20 and of the electromagnetic clutch 37 aredirectly controlled by means of a relay device 39, which in its turn isbrought into operation when the operator on the car grounds thecontrolling conductor 21 in a suitable manner.

The relay device consists of a solenoid 40, operating upon a core 41,'towhich a suitable circuit-closing device is attached. In the arrangementshown the circuit-closing device consists of a plate 42, which in oneposition connects the fixed contacts 43 and 44, while in its otherposition it connects the fixed contacts 45 and 46. The relay device isvertically arranged, so that the action of gravity retains thecontact-plate 42 in position to connect the fixed contacts 43 and 44when there is no current in the solenoid or insufficient current to liftits core and attached parts. When, on the other hand, sufficient currentflows through the circuit, the action of gravity is overcome, and theplate 42 connects the fixed contacts 45 and 46, the plate being returnedto its original position when the current in the solenoid issufficiently reduced or is interrupted.

The connections of the motor-terminals are as follows: One of theterminals is connected to one of the lower fixed contacts 43, another toa fixed contact 45 immediately above, while the third is not connectedto any of these fixed contacts, but directly to the secondary main 31 ofthe supply-transformer 29. The

magnetizing-coil 37 of the magnetic clutch has one of its terminalsconnected to one of the lower fixed contacts 44, while its otherterminal is joined to the main 31. The actuating-circuit 40 of the relaydevice 39 has one terminal connected to the fixed contact 43, to whichone of the terminals of the driving-motor is also connected, its otherterminal being connected, through a suitable lead 47, with thecontrolling-conductor 21, arranged along the railway.

The motor 20 is arranged, as already described, so as to rotate thecontrolling-switch 22 in one direction, while in order to produce areverse direction of rotation I employ some suitablemeanssuch,forexample,as a spring or weight. In the instance shown aweight WV is employed, the same being suspended from a cord passing overa pulley on the shaft of the cylinder. A pin 48, carried by the cylinderor the switch, is adapted to engage a fixedeastic buffer 48, whichserves as a stop to limit the motion of the switch-cylinder in eitherdirection.

The controlling-circuit on the railWay-ve hicle consists of a resistanceR, having two terminals connected, respectively, to fixed contacts 4950, one terminal of the resistance R being also connected to acontact-shoe 51, arranged to slide along the controlling-condoctor 21. Aswitch 52 is arranged so as to connect either of the fixed contacts 49and 50 to ground, as shown at G.

In starting the motor (indicated at M) the operator first closes theswitch upon the con- .tact 50, thereby causing current to pass throughthe solenoid 40 and through the magnetizing-coil 37 on the magneticclutch, the circuit being completed through the conductor 31 of thetransformer 29 and the respective ground connections of saidtransformer. The resistance is so chosen that the solenoid 40 does notcause its core to be lifted, although at the same time the currentthrough the magnetic clutch is sufficient to cause the same to bebrought into action. This step in the operation is ineffective instarting, being of use only in subsequent operations. The switch 52 istherefore moved rapidly over the contact 50 and to contact 49, where itis allowed to remain until the vehicle has been brought up to normalspeed, this operation taking place in the following manner: Theresistance B being cut out, a stronger current flows through thesolenoid 40, thereby causing the contact-plate 42 to be lifted andbrought into engagement with the fixed contacts 45 and 46. By thisoperation one of the terminals of the motor is connected directly toground throughthe lead 47, while the other two terminals are then inconnection with the secondary mains 30 and 31 of the supplytransformer29. ply-transformer being also grounded completes the connections to themotor, and the same therefore starts up and runs, thereby causing a slowrotation of the controllingswitch 22. The working conductors 5 6 arethen progressively connected with circuits of different frequenciesuntil they are finally The other main of the sup-v brought intoconnection with the mains of the supply-transformer 29 in a manneralready described. After these connections have been effected thecontrolling-switch 52 is moved back to the contact 50, thereby causingthe circuit of the motor 20 to be broken, at the same time completingthe circuit through the magnetic clutch 38, whereupon the motor isstopped and locked in position. When it is desired to stop therailway-vehicleby progressively decreasing the frequency of currentsupplied to the working conductors 5 and 6, all that is necessary is tomove the switch 52 off the contact 50, so as to break thecontrolling-circuit. The magnetic clutch is then released, and theweightW or other energy-storing device causes a rev-arse movement of theswitch-cylinder, thereby producing an inversely-progressing change inthe frequency of current supplied to the working conductors untilfinally the current has been interrupted altogether.

Various important advantages accrue from the use of a system operatingin the manner above described. Thus, for example, when the frequency ofcurrent in the supply system is progressively increased in order tostart the motor or motors connected thereto the result, so far asstarting torque is concerned, is practically the same in effect as thatsecured by the use of a variable resistance in the secondary of themotor, without, however, involving the waste of energy incident thereto.There is this difference, however, that With a low frequency, althoughthe starting torque may be made equal to or greater than that at ahigher frequency with resistance in the secondary of the motor, themaximum attainable speed of the motor at this low frequency iscorrespondingly low. To get an increase in speed, it is thereforenecessary to increase the frequency, and in the arrangement above shownthis increase is made progressive, so that the rate of acceleration mayhave some approximation to uniformity.

In stopping the motors fed from the working conductors thefrequency-varying means presents valuable advantages in that it permitsthe motors to act as generators, thereby serving as powerful brakes, atthe same time returning to the line the energy which would otherwise belost in the brake-shoes. If the motor or motors be running at normalspeed, then if the frequency of current in the working conductors bereduced by a suitable amount less than that corresponding to the speedof the motors the motors will act as induction-generators, since theywill then be running at a speed above synchronism. The

braking effect which results will then act, of course, to reduce thespeed of the motors and the vehicle or vehicles driven thereby, so thatthe speed of the motors drops until the motors run below the value ofspeed corresponding to synchronism at the reduced frequency. At or aboutthis time the frequency on the working conductors may be reduced anotherstep, thus repeating the operation described, and this cycle ofoperations may be continued until the lowest frequency available isbrought into use,whereupon the circuit may be interrupted altogether.These changes may be caused to take place at regularly-recurringintervals by allowing the switch-opcrating mechanism to act continuously, or the changes may be made step by step, with any desiredinterval between each step, by suitably manipulating thecontrolling-switch 52 on the car.

Since the section comprising the conductors 5 6 and similarly-operatedsections are normally dead, the controlling-conductor 21 is extendedalong the adjacent sections, so that as a car approaches a normally deadsection the operator on the car by closing the circuit of thecontrolling-conductor, as described, may bring the said section up tonormal frequency prior to the time the car runs into that section. Whensuch section is reached, the frequency of current supplied to conductorsof that section may be reduced in the manner described.

It will be evident that my invention is susceptible of manymodifications and adaptations, and for this reason I do not Wish myclaims to be construed in a limited sense, but rather to be extended soas adequately to protect my invention.

That I claim as new, and desire to secure by Letters Patent of theUnited States, is

1. The combination of working conductors, an alternating-current motor,traveling current-collecting means connecting said Working conductorsand motor, and means controlled from the vicinity of the motor forvarying the frequency of current supplied to said working conductors.

2. In an electric-railway system, the combination of acurrent-conducting system, a railway-vehicle, and means on said vehiclefor controlling the frequency of current supplied to saidcurrent-conducting system.

3. The combination of a plurality of generators, a motor, and anelectrically-controlled switch for connecting the supply-circuits ofsaid motor with any one of said generators.

4. The combination of working conductors, an alternating-current motor,traveling current-collecting means for operatively connecting saidworking conductors and motor, and a switching mechanism controlled fromthe vicinity of said motor for varying the frequency of current suppliedto said working conductors.

5. The combination of working conductors, a multiphasealternating-current motor, travelingcurrent-collecting means foroperatively connecting said working conductors and motor, and aswitching mechanism controlled from the vicinity of said motor forvarying the frequency of current supplied to said working conductors.

6. The combination of working conductors,

an alternating-current motor, traveling current-collecting means foroperatively connecting said working conductors and motor, and anelectrically-controlled switching mechanism for controlling thefrequency of current supplied to said working conductors.

7. In an electric-railway system, the combination of acurrent-conducting system extending along the railway, anelectricallydriven vehicle adapted to receive energy from saidcurrent-conducting system, and means.

on said vehicle for controlling the frequency of current supplied tosaid current-conducting system.

8. In an alternating-current electric-railway system, the combination ofa current-conducting system extending along the railway, anelectrically-actuated vehicle on said railway, and means controlled fromsaid vehicle for progressively increasing or decreasing the frequency ofcurrent supplied to said currentconducting system.

9. In an electric-railway system, the combination of acurrent-conductingsystem extending along the railway, means forgenerating currents of different frequencies, and anelectrically-controlled switch for governing the supply of said currentsto said current-conducting system.

10. In an electric-railway system, the combination of conductorsextending along the railway, means for generating currents of differentfrequencies, and an electricallydriven switch for governing the supplyof said currents to said conductors.

11. In an electric-railway system, the combination of supplyconductorsextending along the railway, an electrically-actuated.

vehicle on said railway, a plurality of sources of current, and meanscontrolled from said vehicle forconnecting said supply-conductors withsaid sources of current.

12. In an electric-railway system, the combination of supplyconductorsextending along the railway, an electrically-actuated vehicle on saidrailway, a source of current, and means controlled from said vehicle forconnecting said source of current and said supply-conductors together.

13. The combination of a plurality of sources of current, asupply-circuit, a controlcircuit,and means brought into action throughthe instrumentality of said control-circuit for connecting saidsupply-circuit with any one of said sources of current.

14. In an electric-railway system, the combination of sectionalconductors arranged along the railway, means for supplying one sectionwith current of uniform frequency, and means for supplying anothersection with currents of variable frequency.

15. In an electric-railway system, the com bination of sectionalconductors arranged along the railway, means for supplying one sectionwith current of uniform frequency, and means for supplying anothersection with currents of frequency variable at will.

16. In an electric-railway system,the combination of sectionalconductors arranged along the railway, a vehicle on said railway, andmeans controlled from said vehicle for supplying current of variablefrequency to one of said sections.

17. In an electric-railway system, the combination of working conductorsextending along the railway, a control-conductor also extending alongthe railway, an electricallyactuated vehicle, contacts moving with saidvehicle and engaging said conductors, a switch on the vehicle forcompleting the circuit of said control-conductor, sources of current ofdifferent frequencies, and means responsive to the operation of saidswitch for connecting said working conductors with any one of saidsources.

18. In an electric-railway system, the combination of acurrent-conducting system extending along the railway, acontrol-conductor also extending along the railway, an electrically-actuated vehicle, contacts moving with said vehicle and engaging saidcurrentconducting system and said control-conductor, a switch on thevehicle for completing the circuit of said control-conductor, sources ofon rrent of different frequencies, and means responsive to the operationof said switch for progressively connecting said current-conductingsystem with the different sources of current.

19. In an electric-railway system, the com bination of acurrent-conducting system extending along the railway, acontrol-conductor also extending along the railway, an electricallyactuated vehicle, contacts moving with thevehicle and engaging saidcurrentconducting system and said control-conductor, means on saidvehicle for completing the circuit of said control-conductor, aplurality of sources of current, and means brought into action throughthe instrumentality of the circuit of said control-conductor, forconnecting said current-conducting system with any one of said sources.

20. In an electric-railway system, the combination of acurrent-conducting system extending along the railway, acontrol-conductor also extending along the railway, anelectricallyactuated vehicle, contacts moving with the vehicle andengaging said currentconducting system and said control-conductor, meanson the vehicle for completing the circuit of said control-conductor andfor vary ing the current therein, a plurality of sources of current, andmeans brought into action through the instrumentality of the circuit ofsaid control-conductor for connecting said current-conducting systemwith any one of said sources.

21. In an electric-railway system, the combination of acurrent-conducting system ex tending along the railway, acontrol-conductor also extending along the railway, anelectrically-actuated vehicle, contacts moving with the vehicle andengaging said currentconducting system and said control-conductor, arheostatic switch on the Vehicle for completing the'circuit of saidcontrol-conductor, a plurality of sources of current, and means broughtinto action through the instrumentality of the circuit of saidcontrol-conductor for connecting said current-conducting system with anyone of said sources.

22. In an electric railway, a sectional conducting system, a source ofalternating current of fixed frequency connected to certain of thesections of the conducting system, a plurality of sources of alternatingcurrent of different frequencies, and means for connecting any one ofsaid plurality of sources to another section or sections.

23. In an electric railway, a sectional conducting system, a source ofalternating current of fixed frequency connected to certain of thesections of the conducting system, a plurality of sources of alternatingcurrent of successively-increasing frequencies and means forsuccessively connecting said sources to another section or sections ofthe conducting system.

24. In an electric railway, a sectional conducting system, a source ofalternating current of fixed frequency connected to certain of thesections of the conducting system, means for supplying alternatingcurrents of fixed frequency to certain of the sections of the conductingsystem, and means for supplying currents of successively-varyingfrequency to another section or sections.

25. In an electric railway, a sectional conducting system, a source ofalternating current of fixed frequency connected to certain of thesections of the conducting system, a plurality of sources of alternatingcurrent of different frequencies, a switch for connecting any one ofsaid plurality of sources to another of said sections, and meanscontrollable from a distant point for operating said switch.

26. In an electric-railway system, a motor equipment, a sectionalconducting system for supplying current thereto, a source of alternatingcurrent of fixed frequency connected to certain of the sections of theconducting system, means for supplying currents of successively-varyingfrequency to another section or sections, a device for determining thefrequency to be supplied, electromagnetic means for controlling theoperation of said device, and an operating system for saidelectromagnetic means comprising a suitable source of current, aconductor extending along the railway, a traveling contact cooperatingtherewith, and a switch in operative relation to said contact.

27. In an electric-railway system, a motor equipment, a sectionalconducting system for supplying current thereto, a source of alternatingcurrent of fixed frequency connected to certain of the sections of theconducting system, and means located at certain points along the roadfor supplying currents of successively-varying frequency to the said m0-tor equipment.

In witness whereof I have hereunto set my hand this 25th day of April,1900.

WILLIAM B. POTTER.

Witnesses:

W. M. BROWN, A. L. LONGEE.

